1. Field of the Invention
The present invention relates to a wafer probe station, and more particularly, to a wafer probe station where a tilt of a chuck is controlled so as to allow a uniform load to be applied to the chuck in the case where an eccentric load is applied to the chuck due to overdriving.
2. Background of the Invention
As illustrated in FIG. 1, a wafer probe station in the related art includes a probe unit 11 including a tester 12 which tests a wafer W, a chuck 16 which the wafer W is mounted on, a chuck transporting unit 17 which moves the chuck 16, and a control unit 18 which controls overall operations.
In the wafer probe station 10 in the related art, in the case where a probe card 14 used for the testing is fixed to a DUT board 13 of the wafer probe station 10, the wafer probe station 10 checks positions of contact electrodes P on the wafer and positions of probes 15 of the probe card by using a vision sensor (not shown) such as a CCD camera and controls the probe card 14 and the chuck 16 based on the checked position information. Next, the control unit 18 of the wafer probe station 10 drives the chuck transporting unit 17 based on the checked position information to transport the chuck 16 to a predetermined position so that the probes 15 of the probe card 14 and the contact electrodes P of the wafer mounted on the chuck 16 face each other before the contact for the testing. Next, the control unit 18 of the wafer probe station 10 performs predetermined overdriving control to electrically connect the contact electrodes P of the wafer to the probes 15 through contact there between. In an ideal case, due to the overdriving control, the wafer probe station 10 allows the wafer W mounted on the chuck 16 and the probe card 14 to be in uniform contact with each other by an appropriate pressure.
However, in the wafer probe station 10, due to an error in the mechanical accuracy and external disturbance, it is actually difficult to maintain the wafer W mounted on the chuck 16 and the probe card 14 in a prefect contact state. In this state, although the chuck 16 is lifted up to a height corresponding to the predetermined overdriving amount, a specific position of the wafer may be pressed too deeply, so that the wafer W is impaired, or a specific position may not be correctly pressed, so that there is a problem in that it is impossible to perform normal testing due to the occurrence of ‘open failure’ where the probe 15 and the contact electrode P are not in contact with each other.
In order to solve this problem, in the wafer probe station 10 of the related art, after the wafer and the probe card 14 are in contact with each other, the state of marks pressed on the wafer is visually tested, or the probe card 14 and the chuck 16 on which the wafer W is loaded are adjusted by using a vision sensor.
However, the adjusting method in the related art has a problem in that accurate adjustment cannot be easily performed due to limitation of the control method using a visual sensing result, so that reliability of the testing deteriorates and a problem in that the time taken for the adjustment is elongated, so that the read time of the testing process is increased. In addition, recently, since the size of the wafer W and the degree of integration of parts tend to be further increased, so that the problem according to initial settings of the wafer W with respect to the probe card 14 described above is much worse.